The present invention relates to a display device, and more particularly, to a liquid crystal display device configured to use a backlight equipped with a wavelength converter having semiconductor quantum dots for improving light utilization efficiency.
The liquid crystal display device includes a TFT substrate having pixel electrodes and thin film transistors (TFT) formed in a matrix, a counter substrate which faces the TFT substrate, and a liquid crystal interposed between the TFT substrate and the counter substrate. An image is formed by controlling the luminous transmittance of liquid crystal molecules for each pixel.
The backlight is disposed on the back surface of the liquid crystal display panel since the liquid crystal by itself is unable to emit light rays. The LED (Light Emitting Diode) is employed as the light source for the backlight of the liquid crystal display device for the mobile phone. The LED is disposed on the side surface of the light guide plate, and various types of optical sheets are applied to the light guide plate. The backlight is constituted by storing the above-described optical components in the mold.
Generally, the LED emits the monochromatic light contrary to the requirement of the backlight for the liquid crystal display device to emit white light. Consequently, the LED for emitting UV light or blue light, and the optical converter for generating the light ray with longer wavelength have been employed to constitute the white light emitting structure.
Japanese Unexamined Patent Application Publication No. 2015-106487 discloses the wavelength converter disposed at the light emission side of the LED, which includes the dichroic mirror at the side that faces the LED so as to prevent the light with converted wavelength from returning to the LED for the purpose of preventing reflection of the light with the converted wavelength toward the LED.
Japanese Unexamined Patent Application Publications Nos. 2014-137961, 2002-116440, and 2006-84757 disclose the structure having the reflection sheet disposed behind the LED for the purpose of preventing the light emitted from the LED from leaking out of the back side of the LED serving as the light source. Japanese Unexamined Patent Application Publication No. 2006-184347 discloses the structure having the reflection sheet disposed behind the cold-cathode tube for the purpose of preventing the light from leaking out of the back side of the cold-cathode tube serving as the light source.